1. Field of the Invention
The present invention relates generally to a process for the polymerization of a feedstock containing one or more C3 to C20 1-olefins in the presence of a solid, unsupported metallocene- and activator-containing catalyst system to form a viscous oligomer oil.
2. Discussion of the Prior Art
Slaugh et al., U.S. Pat. No. 4,658,078 (Apr. 14, 1987), discloses a process for producing relatively low molecular weight dimers by dimerizing alpha olefins to vinylidene olefins by contacting the alpha olefins with a soluble catalyst comprising a metallocene and an aluminoxane. However, the use of a soluble catalyst necessitates a wash step for the removal of catalyst from the polymerization product and the use of a hazardous solvent such as toluene generally required in soluble metallocene catalyst systems. Consequently, efforts have been made to prepare and use heterogeneous or solid metallocene catalyst systems. The solid systems employed have generally involved immobilization of the metallocene and/or aluminium compound serving as the activator on an inorganic support. Such systems suffer from the disadvantage of requiring the use of support material, and are generally of lower activity than soluble catalyst systems.
Consequently, it is highly desirable to be able to prepare and use unsupported solid metallocene catalyst systems with comparable (minimal loss) of catalyst activity. Herrmann et al., U.S. Pat. No. 5,914,376 (Jun. 22, 1999), discloses a process for the polymerization of an olefin in the presence of an unsupported heterogeneous metallocene catalyst system to form a solid polymer. The solid catalyst system is obtained by reacting a soluble metallocene with a solid aluminoxane which is obtained as a by-product obtained in the preparation of toluene-soluble aluminoxanes.
Turner, U.S. Pat. No. 4,752,597 (Jun. 21, 1988) discloses a process for preparing a solid, unsupported matellocene catalyst system. The metallocene catalyst system comprises the metallocene and aluminoxane. The metallocene and aluminoxane are contacted at a mole ratio of aluminoxane to metallocene of from about 12:1 to about 100:1 and reacted in a hydrocarbon solvent in which the metallocene and aluminoxane are each soluble but in which the resulting solid product is insoluble. The metallocene and aluminoxane are reacted at a temperature in the ranges of xe2x88x9278xc2x0 C. to about 50xc2x0 C. The resulting solid catalyst is generally sparingly soluble oils at ambient temperature in aromatic solvents, insoluble solids in aliphatic solvents, and decomposes in polar solvents. Upon recovery, the resulting catalyst system was a glassy solid in most of the patent""s examples.
Kioka et al., U.S. Pat. No. 4,923,833 (May 8, 1990) discloses five methods for preparing an unsupported solid olefin polymerization catalyst containing a Group IVB metal-containing metallocene component and an aluminoxane component. Three of the methods involve the use of a solvent in which the aluminoxane is insoluble or sparingly soluble. The remaining two methods involve spray drying a solution either of the aluminoxane alone or of the metallocene and aluminoxane together. In Comparative Example 1, the preparation method of the invention is contrasted with a method of preparing an unsupported solid catalyst containing a metallocene and methylaluminoxane by combining a solution of the metallocene in toluene with a solution of methylaluminoxane in toluene and completely evaporating the toluene. Thus, Comparative Example 1 did not employ a solvent in which the methylaluminoxane was only sparingly soluble. The resulting solid catalyst particles had non-uniform shapes, a low specific surface area, and a broad particle size distribution. When used for the polymerization of ethylene to form polyethylene, the comparative catalyst had a substantially lower polymerization activity and resulted in the production of polyethylene having a substantially lower bulk density than when the catalyst of the invention was employed. There is no suggestion or recommendation in U.S. Pat. No. 4,923,833 that the comparative catalyst be used as a polymerization catalyst at all or more particularly as a polymerization catalyst for the production of a viscous oligomer oil.
It is therefore a general object of the present invention to provide an improved polymerization process employing an unsupported insoluble metallocene catalyst system that overcomes the aforesaid problems of prior art processes.
More particularly, it is an object of the present invention to provide a process for using an unsupported insoluble metallocene catalyst system it in the polymerization of one or more linear C3 to C20 1-olefins to produce a product mixture comprising an essentially terminally unsaturated viscous, essentially 1-olefin poly (1-olefin) or copoly (1-olefin) of molecular weight between about 300 and 10,000 that exhibits a terminal vinylidene content of more than 50%.
Other objects and advantages will become apparent upon reading the following detailed description and appended claims.
These objects are achieved by the process of the present invention for the production of an oligomer oil comprising:
(i) polymerizing a feed comprising one or more linear C3 to C20 1-olefins having at least one hydrogen on the 2-carbon atom, at least two hydrogens on the 3-carbon atom and at least one hydrogen on the 4-carbon (if at least 4 carbon atoms are present in the olefin), in the presence of a solid metallocene catalyst system comprising a bulky ligand transition metal complex component of the stoichiometric Formula 1 and an activator comprising an organoaluminum compound or a hydrocarbylboron compound or a mixture thereof:
LmMXnXxe2x80x2pxe2x80x83xe2x80x83Formula 1 
xe2x80x83wherein L is the bulky ligand, M is the transition metal, X and Xxe2x80x2 may be the same or different and are independently selected from the group consisting of halogen or a hydrocarbyl group or hydrocarboxyl group having 1-20 carbon atoms, wherein m is 1-3, n is 0-3, p is 0-3 and the sum of the integers m+n+p corresponds to the transition metal valency, to thereby form a viscous oligomer oil product mixture comprising an essentially terminally unsaturated viscous, essentially 1-olefin-containing poly (1-olefin) or copoly (1-olefin) of molecular weight between about 300 and about 10,000 that exhibits a terminal vinylidene content of more than 50%; wherein the aforesaid solid metallocene catalyst system is formed by a process comprising:
(a) combining in an organic solvent boiling below about below 250xc2x0 C. and a soluble metallocene and a soluble activator comprising at least one of an organoaluminum and a hydrocarbylboron to form a soluble metallocene- and activator-containing catalyst system; and
(b) removing the aforesaid solvent to thereby form the aforesaid catalyst system as a solid. The present invention is also the solid metallocene- and activator-containing catalyst system formed by the process of the present invention.
A preferred embodiment the present invention involves producing a viscous oligomer oil having predetermined properties by (ii) oligomerizing at least a pre-selected fraction of the product mixture formed in the aforesaid polymerization step (i) in the presence of an acidic oligormerization catalyst to thereby form the aforesaid oligomer oil, wherein the resulting product mixture comprises less than 35% oligomers that contain two or less monomeric units and at least 60% of oligomers that contain at least three monomeric units.
The metallocene catalyst employed in preparing an unsupported insoluble metallocene catalyst system in step (a) of the method of this invention, comprises a bulky ligand transition metal complex of the stoichiometric Formula 1:
LmMXnX1pxe2x80x83xe2x80x83Formula 1 
wherein L is the bulky ligand, M is the transition metal, X and X1 are independently selected from the group consisting of halogen, hydrocarbyl group or hydrocarboxyl group having 1-20 carbon atoms, and m is 1-3, n is 0-3, p is 0-3, and the sum of the integers m+n+p corresponds to the transition metal valency. The aforesaid metal complex contains a multiplicity of bonded atoms forming a group which may be cyclic with one or more optional heteroatoms. The ligands L and X may be bridged to each other, and if two ligands L and/or X are present, they may be bridged. The catalyst is a metallocene in which M is a Group IV, V or VI transition metal, and one or more L is a cyclopentadienyl or indenyl moiety.
Preferably, the metallocene is represented by the stoichiometric Formula 2:
(Cp)mMR1nR2pxe2x80x83xe2x80x83Formula 2 
wherein each Cp is a substituted or unsubstituted cyclopentadienyl or indenyl ring, and each such substituent thereon can be the same or different and is an alkyl, alkenyl, aryl, alkaryl, or aralkyl radical having from 1 to 20 carbon atoms or at least two carbon atoms formed together to form a part of a C4 or C6 ring; wherein R1 and R2 are independently selected from the group consisting of halogen, hydrocarbyl, hydrocarboxyl, each having 1-20 carbon atoms; and wherein m is 1-3, n is 0-3, p is 0-3, and the sum of m+n+p corresponds to the oxidation state of M.
In alternative preferred embodiments, the metallocene is represented by the stoichiometric Formulas 3 or 4:
(C5R3g)kR4s(C5R3g)MQ3xe2x88x92kxe2x88x92xxe2x80x83xe2x80x83Formula 3 
or 
R4s(C5R3g)2MQ1xe2x80x83xe2x80x83Formula 4 
wherein each C5R3g is a substituted or unsubstituted cyclopentadienyl, wherein each R3 may be the same or different and is hydrogen, alkyl, alkenyl, alkaryl or aralkyl having from 1 to 20 carbon atoms or at least 2 carbon atoms joined together to form a part of a C4 to C6 ring; wherein R4 is either 1) an alkylene radical containing from 1 to 4 carbon atoms, or 2) a dialkyl germanium or silicon or an alkyl phosphoric or amine radical, and R4 is substituting on and bridging two C5R3g rings or bridging one C5R3g ring back to M, wherein each Q can be the same or different and is an alkyl, alkenyl, aryl, alkaryl, or arylalkyl radical having from 1 to 20 carbon atoms or halogen, and Qxe2x80x2 is an alkylidene radical having from 1 to 20 carbon atoms; when k is 0, x is 1, otherwise x is always 0; and wherein s is 0 or 1; and when s is 0, g is 5 and k is 0, 1 or 2; and when s is 1, g is 4 and k is 1. M is a transition metal of Group IV, V or VI, preferably Group IV.
Preferably each C5R3g is a monosubstituted cyclopentadienyl of the type C5H4R3 and each R3 may be the same or different and is a primary or secondary alkyl radical. When R3 is a primary alkyl radical, it is preferably methyl, ethyl or n-butyl. When R3 is a secondary radical, it is preferably isopropyl or sec-butyl. The resulting polymerization product has a viscosity in the range of 2-20 cSt at 100xc2x0 C. In another preferred embodiment, each C5R3g is a di-, tri-, or tetrasubstituted cyclopentadienyl of the type C5H3R32, C5H2R33 or C5HR34, and each R3 may be the same or different primary or secondary radical. The resulting polymerization product has a viscosity of 20-5000 cSt at 100xc2x0 C. In both cases, the reaction is performed at a temperature in the range of from 25 to 150xc2x0 C.
In addition to the bulky ligand transition metal complex, step (a) of the method of this invention also involves an activating quantity of an activator selected from organoaluminum compounds and hydrocarbylboron compounds. Such organoaluminum compounds include fluoro-organoaluminum compounds. Suitable organoaluminum compounds include compounds of the formula AIR503, where each R50 is independently C1-C12 alkyl or halo. Examples include trimethylaluminium (TMA), triethylaluminium (TEA), tri-isobutylaluminium (TIBA), tri-n-octylaluminium, methylaluminiumdichloride, ethylaluminium dichloride, dimethylaluminium chloride, diethylaluminium chloride, ethylaluminumsesquichloride, methylaluminumsesquichloride, and aluminoxanes. Aluminoxanes are well known in the art as typically the oligomeric compounds which can be prepared by the controlled addition of water to an alkylaluminium compound, for example trimethylaluminium. Such compounds can be linear, cyclic or mixtures thereof. Commercially available aluminoxanes are generally believed to be mixtures of linear and cyclic compounds. The cyclic aluminoxanes can be represented by the formula [R51AIO]s and the linear aluminoxanes by the formula R52(R53AIO)s wherein s is a number from about 2 to 50, and wherein R51, R52, and R53 represent hydrocarbyl groups, preferably C1 to C6 alkyl groups, for example methyl, ethyl or butyl groups. Alkylaluminoxanes such as linear or cyclic methylaluminoxanes (MAOs) or mixtures thereof are preferred.
Mixtures of aluminoxanes and trialkylaluminium compounds are particularly preferred, such as MAO with TMA or TIBA. In this context it should be noted that the term xe2x80x9caluminoxanesxe2x80x9d as used in this specification includes aluminoxanes available commercially which may contain a proportion, typically about 10 weight percent, but optionally up to 50 weight percent, of the corresponding trialkylaluminium, for instance, commercial MAO usually contains approximately 10 weight percent trimethylaluminium (TMA), while commercial MMAO contains both TMA and TIBA. Quantities of aluminoxanes quoted herein include such trialkylaluminium impurities, and accordingly quantities of trialkylaluminium compounds quoted herein are considered to comprise compounds of the formula AIR3 additional to any AIR3 compound incorporated within the alkylalumoxane when present.
Examples of suitable hydrocarbylboron compounds are boroxines, trimethylboron, triethylboron, dimethylphenylammoniumtetra(phenyl)borate, trityltetra(phenyl)borate, triphenylboron, dimethylphenylammonium, tetra(pentafluorophenyl)borate, sodium tetrakis[(bis-3,5-trifluoromethyl)phenyl]borate, trityltetra(pentafluorophenyl)borate and tris(pentafluorophenyl) boron.
In the preparation of the catalysts of the present invention, the quantity of activating compound selected from organoaluminium compounds and hydrocarbylboron compounds to be employed is easily determined by simple testing, for example, by the preparation of small test samples which can be used to polymerise small quantities of the monomer(s) and thus to determine the activity of the produced catalyst. It is generally found that the quantity employed is sufficient to provide 0.1 to 20,000 atoms, preferably 1 to 2000 atoms, of aluminum or boron per atom of the transition metal in the compound of Formula 1. Generally, from about 1 mole to about 5000 moles, preferably at least 150 moles of activator are employed per mole of transition metal complex.
In step (a) of the method of the present invention the metallocene catalyst and activator are combined in a suitable organic solvent at a temperature in the range of from about xe2x88x9240 to 150xc2x0 C., preferably from about 0 to 100xc2x0 C. and more preferably from about 20 to 80xc2x0 C., The metallocene catalyst and activator can initially exist together in the same solution or can initially exist in separate solutions which are then combined. Suitable solvents for use with the metallocene catalyst and/or the activator boil in the range of from xe2x88x9240 to 250xc2x0 C., preferably from about 0 to 200xc2x0 C., and most preferably from about 30 to 150xc2x0 C. at 1 atmosphere pressure. Suitable solvents include C4-C14 aliphatics and monoolefins, light aromatics, alkyl substituted aromatics, halogenated aromatics and aromatic ethers. Preferably the solvent(s) employed include C4-C10 alkanes, C4-C10 mono-olefins, benzene and alkyl substituted benzenes, halogenated aromatics, and aromatic ethers. More preferably the solvent(s) employed include benzene, toluene, xylenes, ethylbenzene, chlorobenzene, C5-C7 alkanes and mono-olefins such as 1-octene and 1-decene. Typically the solvent(s) employed are benzene, toluene, xylenes, and C5-C7 alkanes.
In step (b) of the method of the present invention, the solvent is removed by any convenient conventional technique. Evaporation, optionally under reduced pressure, centrifugation and separation of the liquid from the resulting solid, and spray drying are examples of suitable techniques for converting the dissolved metallocene catalyst and activator to the solid form and separating and recovering the resulting solid from the liquid. Preferably the solid is recovered by evaporation in its dry form.
The solid catalyst system can then be used for polymerization/oligomerization in its solid state, or it can be slurried in a nonvolatile liquid after the aforesaid solvent is removed. Suitable nonvolatile liquids for use as such slurry liquids include C10-C30 hydrocarbons, aromatics with a boiling point between 125xc2x0 C. and 300xc2x0 C., halogenated aromatics, and aromatic ethers. Preferably the slurry liquid is a C14 to C24 hydrocarbon.
The polymerization conditions employed in polymerization step (i) of the polymerization/oligomerization method of this invention is slurry phase and either batch, continuous or semi-continuous, with polymerization temperatures ranging from xe2x88x92100xc2x0 C. to +300xc2x0 C. In the slurry phase polymerization process, the solid particles of catalyst are fed to a polymerization zone either as dry powder or as a slurry in the polymerization diluent. Preferably, the particles are fed to a polymerization zone as a suspension in the polymerization diluent. The polymerization zone can be, for example, an autoclave or similar reaction vessel, or a continuous loop reactor, e.g. of the type well-known in the manufacture of polyethylene by the Phillips Process.
Step (i) of the present invention can be operated under batch, semi-batch, or so-called xe2x80x9ccontinuousxe2x80x9d conditions by methods that are well known in the art. The polymerization process of the step (i) of the method of the present invention is preferably carried out at a temperature above 0xc2x0 C., more preferably above 15xc2x0 C. and most preferably in the range of 25-150xc2x0 C. Adjustment of the polymerization temperature within these defined temperature ranges can provide a useful means of controlling the average molecular weight of the produced polymer. It is also preferred to conduct step (i) under relatively low hydrogen partial pressures, more preferably less than 100 psi and most preferably less than 50 psi.
Monomers that are suitable for use as the olefin that undergoes reaction in step (i) of the process of the present invention are alpha-olefins which have (1) at least one hydrogen on the 2-carbon atom, (2) at least two hydrogens on the 3-carbon atoms, and (3) at least one hydrogen on the 4-carbon (if at least 4 carbon atoms are present in the olefin). Preferably such monomers contain from four to twenty carbon atoms. Thus, suitable alpha-olefin monomers include those represented by the formula H2Cxe2x95x90CHR60 wherein R60 is a straight chain or branched chain alkyl radical comprising 1 to 18 carbon atoms and wherein any branching that is present is at one or more carbon atoms that are no closer to the double bond than the 4-carbon atoms. R60 is an alkyl, preferably containing from 2 to 19 carbon atoms, and more preferably from 2 to 13 atoms. Therefore, useful alpha-olefins include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene and mixtures thereof. Preferably the olefin undergoing reaction contains from four to twenty carbon atoms.
Step (i) of the process of the present invention is controlled to make viscous polymer having a number average molecular weight of not greater than 15,000 and typically from 300 to 10,000, and preferably from 400 to 8,000. The number average molecular weight for such polymers can be determined by any convenient known technique. One convenient method for such determination is by size exclusion chromatography (also known as gel permeation chromatography, GPC) which additionally provides molecular weight distribution information (see W. W. Yau, J. J. Kirkland and D. D. Bly, xe2x80x9cModern Size Exclusion Liquid Chromatographyxe2x80x9d, John Wiley and Sons, New York, 1979). The molecular weight distribution (Mw/Mn) of the polymers or copolymers produced in step (i) is typically less than 5, preferably less than 4, more preferably less than 3, e.g., between 1.5 and 2.5.
The polymers produced in step (i) of this invention are further characterized in that at least about 50% or more of the polymer chains possess terminal ethylenylidene-type unsaturation. A minor amount of the polymer chains can contain terminal vinyl unsaturation, that is, POLY-CHxe2x95x90CH2, and a proportion of the polymers can contain internal monounsaturation, for example, POLY-C(T1)xe2x95x90CH(T2), wherein T1 and T2 are each independently an alkyl group containing 1 to 18, preferably to 8 carbon atoms and POLY represents the polymer chain. The polymer products of step (i) of this inventive process comprise chains which can be saturated by hydrogen, but preferably contain polymer chains wherein at least 50, preferably at least 60, and more preferably at least 75 percent (e.g., 75-98%), of which exhibit terminal ethenylidene (vinylidene) unsaturation. The percentage of polymer chains exhibiting terminal ethenylidene unsaturation may be determined by Fourier Transform Infrared (FTIR) spectroscopic analysis, titration, proton (H)NMR, or C13NMR.
In one preferred embodiment, step (i) is conducted under slurry phase conditions using a catalyst system comprising a catalyst of Formula 2, 3 or 4, in which M is a Group IVb transition metal, typically titanium, zirconium or hafnium, and aluminoxane is an activator with the molar ratio of aluminoxane to metallocene of 150 or greater, and C3-C20 alpha-olefins in a feedstock containing more than 1 weight percent of at least one volatile hydrocarbon liquid but consisting essentially of the C3-C20 alpha-olefins, are polymerized to form an essentially terminally-unsaturated, viscous, essentially-1-olefin-containing poly(1-olefin) or copoly(1-olefin), having a terminal vinylidene content of more than 50%.
In this preferred embodiment, the terminally unsaturated, viscous polymer product of this invention is essentially a poly(1-olefin) or copoly(1-olefin). The polymer chains of the viscous polymers produced in step (i) of the method of this invention are essentially terminally-unsaturated. By essentially terminally-unsaturated is meant that preferably more than about 90% of the polymer chains contain unsaturation, more preferably more than about 95% of the polymer chains in the product polymer contain terminal unsaturation.
In general, the products produced in step (i) are mixtures whose components and their relative amounts depend upon the particular alpha-olefin reactant, the catalyst and reaction conditions employed. Typically, the products are unsaturated and have viscosities ranging from about 2 to about 5000 cSt at 100xc2x0 C. At least a portion of the product mixture generally has the desired properties, for example, viscosity, for a particular application. The components in such portion are usually hydrogenated to improve their oxidation resistance and are known for their superior properties of long-life, low volatility, low pour points and high viscosity indices, which make them a premier basestock for state-of-the-art lubricants and hydraulic fluids.
However, usually such product mixture includes substantial amounts of unreacted olefin feed as well as lower oligomers, particularly dimers which do not have the desired properties or do not include the relative amounts of each viscosity product which correspond to market demand. Thus, step (i) is often performed under conditions that are necessary to produce a product mixture that contains an undesired excess or inadequate amount of one product in order to obtain the desired amount of another product.
A preferred embodiment of the process of the present invention solves this problem by fractionating the product mixture produced in polymerization step (i) in order to separate and recover one or more fraction, containing the components having the desired properties and separating one or more other fraction of the product mixture for additional processing in oligomerization step (ii) of the method of this invention. In a less preferred alternative, the entire product from polymerization step (i) can be oligomerized in step (ii).
The fraction(s) selected for additional processing is then subjected to oligomerization conditions in contact with an oligomerization catalyst in step (ii) such that a product mixture containing at least one product having desired properties and in a desired amount that is not produced in step (i). Typically, the low molecular weight fraction, preferably comprising the monomeric and dimeric components thereof, of the product of step (i) is separated and oligomerized in step (ii). In three alternative preferred embodiments, in one case, the monomeric and dimeric components of the product of step (i), in a second case, the dimeric components of the product of step (i) and in a third case, the dimeric and a portion of the trimeric components (with or without monomeric components) of the product of step (i) are separated and oligomerized in step (ii). Thus, oligomerization step (ii) permits the olefin feed to polymerization step (i) to be converted with greater efficiency to desired amounts of products having desired properties. Thus, the method of the present invention permits improved control of the makeup of the feed and permits a wide range of customer specific oligomer oil products to be produced.
For example, the higher molecular weight portion of the product of polymerization step (i) has advantageous properties when compared to products that are currently in the marketplace. To illustrate, when 1-decene is employed as the feedstock to step (i), the higher molecular weight portion of the product of step (i) is primarily C30+ and has advantages relative to a polyalphaolefin having a viscosity of 6 cSt or higher because it has a higher viscosity index than the polyalphaolefin having a comparable viscosity.
However, the remaining lower molecular weight portion of the product step (i) is a relatively large volume of low value and lighter oligomeric (primarily dimer and unreacted monomer) fraction. A preferred embodiment of the method of this invention serves to upgrade this lower molecular weight portion of the product of polymerization step (i), which is separated from the aforesaid higher molecular weight portion by any convenient conventional means, for example, distillation, and is then upgraded in oligomerization step (ii). For example, when 1-decene is employed as the feedstock to step (i) and when the portion of the product of step (i) containing 20 carbon atoms and less is employed as the feed or portion of the feed to step (ii), this low molecular weight portion from step (i) is converted in step (ii) to a product mixture in which at least 60%, preferably over 70%, and most preferably over 80% of this crude product mixture contains 30 carbon atoms or greater. The product mixture of step (ii) also contains at most 25%, and preferably not more than 15% of carbon numbers greater than or equal to C50; preferably the product mixture of step (ii) contains less than 25%, and more preferably less than 15% of carbon numbers greater than or equal to C40. The product of step (ii) has sufficiently low volatility, a sufficiently high viscosity index, a desirable viscosity in the range of 4 to 5.5 cSt at 100xc2x0 C. and less than 5500 cSt at xe2x88x9240xc2x0 C., and a sufficiently low pour point to serve as base fluids or portions of base fluids for 0W- and 5W- passenger car motor oils and heavy-duty diesel oils. Generally, engine oil formulations and, more particularly 0-W and 5-W engine oil formulations, that comprise at least the fraction of the product mixture of step (ii), at least 60 weight percent of which are oligomers that contain three monomeric units (as defined below), are especially advantageous.
Any suitable oligomerization catalyst known in the art, especially an acidic oligomerization catalyst system, and especially Friedel-Crafts type catalysts such as acid halides (Lewis Acid) or proton acid (Bronsted Acid) catalysts can be employed as the oligomerization catalyst of step (ii). Examples of such oligomerization catalysts include but are not limited to BF3, BCl3, BBr3, sulfuric acid, anhydrous HF, phosphoric acid, polyphosphoric acid, perchloric acid, fluorosulfuric acid, aromatic sulfuric acids, and the like. Like the catalyst employed in step (i), the oligomerization catalyst can be unsupported or supported (absorbed or adsorbed or chemically bound) on a convenient conventional support material. Preferably the oligomerization catalyst is supported. Suitable support materials and their characteristics and impregnation techniques are well known in the art.
Such oligomerization catalysts can be used in combination and with promoters such as water, alcohols, hydrogen halide, alkyl halides and the like. A preferred catalyst system for the oligomerization process of step (ii) is the BF3-promoter catalyst system. Suitable promoters are polar compounds and preferably alcohols containing about 1 to 10 carbon atoms such as methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, n-hexanol, n-octanol and the like. Other suitable promoters include, for example, water, phosphoric acid, fatty acids (e.g., valeric acid) aldehydes, acid anhydrides, ketones, organic esters, ethers, polyhydric alcohols, phenols, ether alcohols and the like. The ethers, esters, acid anhydrides, ketones and aldehydes provide good promotion properties when combined with other promoters which have an active proton e.g. water or alcohols.
Amounts of promoter are used which are effective to provide good conversions in a reasonable time. Generally, amounts of 0.01 weight percent or greater, based on the total amounts of olefin reactants, can be used. Amounts greater than 1.0 weight percent can be used but are not usually necessary. Preferred amounts range from about 0.025 to 0.5 weight percent of the total amount of olefin reactants. Amounts of BF3 are used to provide molar ratios of BF3 to promoter of from about 0.1 to 10:1 and preferably greater than about 1:1. For example, amounts of BF3 of from about 0.1 to 3.0 weight percent of the total amount of olefin reactants are employed.
The amount of catalyst used can be kept to a minimum by bubbling BF3 into an agitated mixture of the olefin reactant only until an xe2x80x9cobservablexe2x80x9d condition is satisfied, i.e. a 2xc2x0-4xc2x0 C. increase in temperature. Because the vinylidene olefins are more reactive than vinyl olefin, less BF3 catalyst is needed compared to the vinyl olefin oligomerization process normally used to produce PAO""s.
The high degree of vinylidine type unsaturation of the product of step (i) when catalysts of Formula 2, 3, or 4 are used makes the product very reactive in the oligomerization of step (ii). In addition, since either the entire amount of product of polymerization step (i) or one or more preselected fractions of it can be oligomerized in step (ii), it is possible in the method of this invention to tailor the feedstock to step (ii) in order to produce the desired relative amounts of each viscosity product desired without producing an excess of one product in order to obtain the desired amount of another product which is desired.
A further embodiment of the method of this invention is to co-oligomerize in step (ii) a pre-selected fraction of the product of step (i) with at least one vinyl olefin containing 4 to 20 carbon atoms. This allows for conversion of a fraction of the product of step (i) which may not be useful, for example, the dimer fraction, to a higher fraction, for example, a trimer fraction, which is useful. The addition of a different vinyl olefin than used in polymerization step (i) to the feed of oligomerization step (ii) permits further control of the make-up of the feed to step (ii), and an even wider range of customer specific oligomer oils to be produced. It also allows for production of an oligomer fraction which could not easily be made from other means, for example, co-oligomerizing the C20 polymer from step (i) with C12 vinyl olefin in step (ii) to form primarily a C32 product. In addition, the distribution of products is highly peaked in favor of oligomers having three monomeric units and requires minimal fractionation. The identity of the vinyl olefin employed and the relative amounts of vinyl olefin and aforesaid fraction of the product mixture of step (i) in step (ii) can be varied to control the amount of products formed in step (ii).
Suitable vinyl olefins for use as additional compounds to be added to the feed to step (ii) in the process contain from 4 to about 30 carbon atoms, and, preferably, about 6 to 20 carbon atoms, including mixtures thereof. Non-limiting examples include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like. Pure vinyl olefins or a mixture of vinyl olefins and vinylidene and/or internal olefins can be used. Usually, the feed contains at least about 85 weight percent vinyl olefin. Additionally, step (ii) can be run so that only a fraction of the vinyl olefin reacts with the preselected polymer fraction from step (i).
The oligomerization of step (ii) is very specific for the formation of an oligomer containing three monomeric units. The product mixture formed in step (ii) contains less than 35%, preferably less than 25%, more preferably less than 15% by weight of oligomers that contain two or less monomeric units. The product mixture formed in step (ii) also contains at least 65%, preferably at least 75%, more preferably at least 85% by weight of oligomers that contain three or more monomeric by weight units, and less than 20%, preferably less than 15% more preferably less than 10% of four or more monomeric units. Thus, the product mixture formed in step (ii) generally contains at least 60%, preferably at least 65%, more preferably at least 70%, and most preferably at least 80% by weight of oligomers having three monomeric units.
As employed in this context, the term xe2x80x9cmonomeric unitsxe2x80x9d is intended to mean both the monomer(s) employed in the feed to polymerization step (i) and the monomer(s) added in oligomerization step (ii) to the portion of the product from step (i) that is employed as the feed to step (ii). Each such monomer can be the source of one or more of the monomeric units that make up an oligomer in the product produced in step (ii). Thus, if no additional vinyl olefinic monomer is added to the portion of the product from step (i) that is employed in the feed to step (ii), the monomers employed in the feed to step (i) are the source of all of the monomeric units in the products formed in step (ii). However, if one or more vinyl olefinic monomers are added to the portion of the product from step (i) that is employed in the feed to step (ii), both such monomers added in step (ii) and the monomers employed in the feed to step (i) are sources of the monomeric units in the products formed in step (ii).
For example, if 1-decene is the feed to step (i) and no other vinyl monomer is added to the feed to step (ii), the oligomers formed in step (ii) and having three monomeric units are trimers of 1-decene. However, if 1-decene is employed as the feed to step (i) and 1-dodecene is added to the feed to step (ii), then the oligomers formed in step (ii) and having three monomeric units have 30, 32, 34 or 36 carbon atoms, with the relative amounts of each depending upon the relative amount of 1-dodecene added.
By varying the choice of the fraction of the product of step (i) that is employed in the feed to step (ii) and of the vinyl olefin added in step (ii), customer-specific oligomer oil products can be produced. For example, the viscosity of such a product can be varied by changing the amount and type of vinyl olefin added to the reaction mixture for the second step. A range of molar ratios of aforesaid pre-selected fraction of the product of step (i) to the vinyl olefin added can be varied, but usually at least a molar equivalent amount of vinyl olefin to the dimeric portion of the aforesaid pre-selected fraction of the product of step (i) is used in order to consume the dimeric portions of the aforesaid pre-selected fraction of the product of step (i). The product oils have viscosities of from about 1 to 20 cSt at 100xc2x0 C. Preferably, mole ratios of from about 10:1 to 1:1.5 and most typically about 1.3:1 of the added vinyl olefin to the aforesaid pre-selected fraction of the product of step (i) are used for the feed to step (ii). The vinyl olefin is typically added at a time when at least about 30 percent by weight of the aforesaid pre-selected fraction of the product of step (i) has been oligomerized in step (ii).
Oligomerization step (ii) can be carried out at atmospheric pressure. Moderately elevated pressures, e.g. to 50 pounds per square inch, can be used and may be desirable to minimize reaction time but are not necessary because of the high reactivity of the vinylidene olefin. Reaction times and temperatures in step (ii) are chosen to efficiently obtain good conversions to the desired product. Generally, temperatures of from about 0xc2x0 to 70xc2x0 C. are used with total reaction times of from about 15 minutes to 5 hours.
The products from step (ii) of the method of the present invention do have the pre-selected desired properties, especially viscosity. Typically, the products of step (ii) are characterized, following removal of unreacted monomer and dimer, by having a viscosity between 3 and 100 cSt, a viscosity index between 110 and 180, a pour point less than xe2x88x9230xc2x0 C., and a Noack volatility at 250xc2x0 C. between 2% and 25%.
When the polymerization step (i) is terminated, the solid catalyst system and liquid product mixture are separated by any convenient conventional solid-liquid separation technique such as filtration, centrifugation, or settling and decantation. The separated viscous oligomer product is recovered essentially free of contamination by residual amounts of catalyst. The separated solid catalysts system can be re-used in a subsequent polymerization step (ii).
The following examples will serve to illustrate certain specific embodiments of the invention disclosed herein. These examples are for illustrative purposes only and should not be construed as limiting the scope of the novel invention disclosed herein as there are many alternative modifications and variations which will be apparent to those skilled in the art and which fall within the scope and spirit of the disclosed invention.